Constant pulse width generator including transition detectors

ABSTRACT

A semiconductor circuit for generating a pulse with a constant pulse width regardless of the pulse widths of the input signals, including a pulse-width fixing circuit for latching the output signal of a gate circuit when an input signal received by the gate circuit changes. The pulse width fixing circuit unlatches the gate circuit a predetermined time after the latching.

BACKGROUND OF THE INVENTION

(1) Field of the Invention

The present invention relates to a semiconductor circuit, more particularly, to a circuit applied in, for example, a static semiconductor memory for generating a clock signal when an input signal, such as the address signal, changes.

(2) Description of the Related Art

A static memory generally does not need a clock signal, in contrast to a dynamic memory, which always needs a clock signal. Some special static memories, however, use clock signals to represent address changes, write instructions, or power downs, to decrease the access time, and so forth. Prior art static memories employing clock signals are disclosed in, for example:

Japanese Unexamined Patent Publication (Kokai) No. 57-69586, published on Apr. 28, 1982, filed on Oct. 15, 1980, inventor: Atsushi Oritani, applicant: Fujitsu Limited;

Japanese Unexamined Patent Publication No. 58-3186, published on Jan. 8, 1983, filed on June 30, 1981, inventor: Atsushi Oritani, applicant: Fujitsu Limited;

Japanese Unexamined Patent Publication No. 58-41485, published on Mar. 10, 1983, filed on Sept. 1, 1981, inventor: Keizo Aoyama, applicant: Fujitsu Limited;

Japanese Unexamined Patent Publication No. 58-41486, published on Mar. 10, 1983, filed on Sept. 1, 1981, inventor: Keizo Aoyama, applicant: Fujitsu Limited;

Japanese Unexamined Patent Publication No. 59-3783, published on Jan. 10, 1984, filed on June 30, 1982, inventor: Atsushi Oritani, applicant: Fujitsu Limited;

Japanese Unexamined Patent Publication No. 59-63091, published on Apr. 10, 1984, filed on Sept. 30, 1982, inventor: Eiji Noguchi, applicant: Fujitsu Limited; and

Japanese Unexamined Patent Publication No. 59-63094, published on Apr. 10, 1984, filed on Oct. 4, 1982, inventor: Keizo Aoyama et al, applicant: Fujitsu Limited.

In the static memories using the clock signals, when a memory cell of the static memory is accessed, a bit-line pair is temporarily short-circuited to be the same potential by applying a clock signal and then is changed to a high level (H) or a low (L) level in accordance with the data stored in the memory cell. This decreases the access time in comparison with a circuit not using a clock signal, wherein the change is effected from an H or L state, depending on the stored data previously read, to an H or L state, depending on the stored data which is to be currently read. This short-circuiting is also effected in a sense amplifier, wherein the response speed for currently read data is increased by resetting the output signals by the clock signal before starting the operation of the sense amplifier.

A clock signal representing a change of an input signal, such as an address signal, is conventionally generated by taking a logical OR of pulses generated by changes of respective input signals. For example, the address signals used for the input signals are 10 bits in a 1K-memory, 11 bits in a 2K-memory, and so forth. From each bit of the address signals, a complementary pair of bit A_(i) and its inverted bit A_(i) (i=0, 1, 2, . . . ) is obtained, which are input to a decoder to act as a signal for selecting a word line or a bit line. A pulse generating circuit for each of the above-mentioned pulses is provided in an address inverter. The pulse generated from the pulse generating circuit is supplied to the OR gate for obtaining the above-mentioned logical OR.

However, the clock signal thus generated has a problem in that, when the rising time and the falling time of the input siganls are indefinite, the width of the clock signal changes depending on the input signals. When the input signals are input address signals, this problem is caused because (1) since the address inverters and, accordingly, the above-mentioned pulse generating circuits are spread over a certain area of a memory chip, the wiring lengths between each pulse generating circuit and the OR gate are different from each other, so that the timings of the output pulses reaching the OR gate are slightly different; (2) since the pulses output from the respective pulse generating circuits do not always have the same pulse widths, the pulse widths of the clock signals and the falling timing of the clock pulses are changed depending on which address signal is changed; (3) there is a case when a plurality of address signals (bits) are changed almost simultaneously but with slightly different timings, and, in this case, since the clock width is a logical sum of the plurality of pulses, the pulse width has a tendency to expand because the pulse widths generated by the respective changes of the address signals are not always the same.

It is not preferable, in order to ensure the short- circuiting of the pair of bit lines and so forth, that the clock pulse width vary depending on which of the input signals or which of the input address signals changes. Therefore, for the above-mentioned reset of the bit line pair or of the sense amplifier, the clock signal is preferred to have a constant pulse width and constant falling and rising timings in response to each change of the input signals.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a semiconductor circuit which can provide a pulse with a constant pulse width in response to each change of input signals.

To attain the above object, there is provided, according to the present invention, a semiconductor circuit including: at least one input-change detecting circuit having a first output end for generating a pulse in response to a change of an input signal; a gate circuit, having an input end operatively connected to the first output end and having a second output end, for changing the signal at the second output end when the input signal changes; and a pulse-width fixing circuit for latching the output signal of the gate circuit in response to a signal change at the second output end of the gate circuit and, a predetermined time after the latching, for resetting the output signal.

BRIEF DESCRIPTION OF THE DRAWINGS

The above object and features of the present invention will be more apparent from the following description of the embodiments with reference to the drawings, wherein:

FIG. 1 is a block diagram of a semiconductor memory chip for explaining the background of the present invention;

FIG. 2 is a circuit diagram of a semiconductor circuit according to an embodiment of the present invention;

FIG. 3 is a circuit diagram of a clock signal generating circuit included in the circuit shown in FIG. 2;

FIGS. 4A through 4F are waveform diagrams for explaining the operation of the circuit shown in FIG. 3;

FIG. 5 is a circuit diagram illustrating an example of a pulse generating circuit included in the circuit shown in FIG. 2; and

FIG. 6 is a circuit diagram illustrating another example of a pulse generating circuit included in the circuit shown in FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 is a plan view of a semiconductor memory chip. In FIG. 1, the semiconductor memory chip CP has a memory cell array MCA, a plurality of address inverters AI₀, AI₁, . . . , and AI_(n), and a clock signal generating circuit CG. Each of the address inverters AI₀, AI₁, . . . , and AI_(n) consists of an address buffer circuit ADB_(i) and a pulse generating circuit PG_(i) , where i=0, 1, . . . , or n. The address buffer circuit ADB_(i) receives an address signal A_(i) to provide a waveform shaped address signal. The pulse generating circuit PG_(i) generates a pulse in response to a change in the address signal A_(i). The outputs of the pulse generating circuits PG₀, PG₁, . . . , and PG_(n) are connected through conducting lines l₀, l₁, . . . , and l_(n) to the inputs of the clock signal generating circuit CG.

Since the lengths of the conducting lines l₀, l₁, . . . , and l_(n) are different from each other, the times necessary to transfer the signals from the pulse generating circuits PG₀, PG₁, . . . , and PG_(n) to the clock signal generating circuit CG are slightly different from each other. This causes the problem of different timings of the generation of the clock signals output from the clock signal generating circuit, as mentioned before.

FIG. 2 is a circuit diagram of a semiconductor circuit according to an embodiment of the present invention. In FIG. 2, A₀, A₁, A₂, . . . are bits of an address for accessing a static memory, and PG₀, PG₁, PG₂, . . . are pulse generating circuits provided in address inverters AI₀, AI₁, . . . (FIG. 1) which receive respective bits A₀, A₁, . . . of the address. Each pulse generating circuit PG_(i) (i=0, 1, 2, . . . ) outputs a pulse having a relatively indefinite width of a low level (hereinafter referred to as L) when the corresponding address bit A_(i) changes from a high level (H) to L or from L to H. PG_(n) is a pulse generating circuit which outputs a pulse when a chip select signal CS drops from the H level to the L level.

The outputs of the pulse generating circuits PG₀, PG₁, PG₂, . . . , and PG_(n) are connected to the gate electrodes of pairs of transistors Q₁₁ and Q₂₁, Q₁₂ and Q₂₂, Q₁₃ and Q₂₃, . . . , and Q_(1n) and Q_(2n), respectively. The pairs of transistors Q₁₁ and Q₂₁, Q₁₂ and Q₂₂, Q₁₃ and Q₂₃, . . . , and Q_(1n) and Q_(2n) each forms a complementary metal oxide semiconductor (CMOS) inverter gate. These CMOS inverter gates constitute a clock signal generating circuit CG of a NAND gate functioning as an OR gate with respect to the L level of at least one of the input signals. That is, when at least one of the pulse generating circuits PG₀, PG₁, . . . , and PG_(n) generates the pulse of the L level, the clock signal generating circuit CG outputs the H level at its output T₁. Since the clock signal generating circuit CG is a NAND gate, when all of the inputs are at the H level, the level of an output end T₁ becomes L. If at least one input is L, the level of the output end T₁ becomes H. Note that the transistors Q₁₁, Q₁₂, . . . , and Q_(1n), which have sources connected to a power supply V_(CC) and illustrated by small circles in the figure, are P-channel metal oxide semiconductor (MOS) transistors. The transistors Q₂₁, Q₂₂, . . . , and Q_(2n) without the small circles are N-channel MOS transistors. The N-channel MOS transistors Q₂₁, Q₂₂, . . . , and Q_(2n) are connected in series. There are the same number of pairs of the P-channel and N-channel MOS transistors Q₁₁ and Q₂₁, Q₁₂ and Q₂₂, . . . , and Q_(1n) and Q_(2n) as pulse generating circuits PG₀, PG₁, . . . , and PG_(n). To the output end T₁, two CMOS inverter gates consisting of P-channel MOS transistors Q₃ and Q₅ and N-channel MOS transistors Q₄ and Q₆ are connected. Thus, a node T₂ of the CMOS inverter consisting of the transistors Q₅ and Q₆ becomes an output end of the clock signal generating circuit CG. In conventional circuits, only the pulse generating circuits PG₀, PG₁, . . . , and PG_(n) and the clock signal generating circuit CG are provided, whereby a clock signal is generated from the output end T₂ whenever any address bit A₀, A₁, . . . changes or the chip select signal CS falls. However, as mentioned before, there was a problem in that the pulse width, particularly the end time (here, the rising edge), of the clock signal generated by the conventional clock signal generating circuit was not always constant.

The generating timings (here, the falling edge) of the clock signals of the pulse generating circuits PG₁, PG₂, . . . are relatively constant. The fluctuations occur in the end timings (here, the rising edge). Because of these fluctuations, the pulse width of the output clock signal was not always constant.

In the present invention, the clock signal generating circuit CG is provided with a circuit WC for making the output pulse width constant. The circuit WC consists of a latch and reset circuit and a control circuit CNT. The latch and reset circuit is constructed by P-channel MOS transistors Q₇ and W₈, connected in series between the power supply terminal V_(CC) and the output end T₁ of the NAND gate, and N-channel MOS transistors Q₉ and Q₁₀ connected in parallel between the source of the transistor Q_(2n) and the ground power supply V_(SS). The control circuit CNT is constructed by P-channel MOS transistors Q₃₁ and Q₃₃, N-channel MOS transistors Q₃₂ and Q₃₄, a resistor R, and a MOS capacitor C, the last two forming an RC delay circuit, as shown in FIG. 2.

FIG. 3 is a circuit diagram of the clock signal generating circuit CG and the pulse width fixing circuit WC included in the circuit shown in FIG. 2. Referring to FIG. 3, in the latch and reset circuit formed by the P-channel MOS transistors Q₇ and Q₈ and the N-channel MOS transistors Q₉ and Q₁₀, the gate of the transistor Q₇ is connected to the output end (node ○2 ) of the inverter formed by the trasistors Q₃ and Q₄. The gate of the transistor Q₈ is connected to the output end (node ○4 ) of the control circuit CNT. The gate of the transistor Q₉ is connected to the output end (node ○2 ) of the CMOS inverter formed by the transistors Q₃ and Q₄. The gate of the transistor Q₁₀ is connected to the output end (node ○4 ) of the control circuit CNT. In the control circuit CNT, the transistors Q₃₃ and Q₃₄ form one CMOS inverter, and the transistors Q₃₁ and Q₃₂ form another. The gates of the transistors Q₃₃ and Q₃₄ function as an input end of the control circuit CNT and are connected to the output end T₁ of the NAND gate. The output of the CMOS inverter formed by the transistors Q₃₃ and Q₃₄ is connected to the gates of the transistors Q₃₁ and Q₃₂. The source of the transistor Q₃₄ is connected through the resistor R to the ground power supply terminal V_(SS). Between the output of the CMOS inverter formed by the transistor Q₃₃ and Q₃₄ and the ground power supply terminal V_(SS) , the CMOS capacitor C is connected. The output of the CMOS inverter formed by the transistors Q₃₁ and Q₃₂ functions as the output of the control circuit CNT.

FIGS. 4A through 4F show the potential changes in respective portions in the circuit shown in FIG. 3. In FIGS. 4A-4F, φ₀ and φ₁ represent pulses generated by the pulse generating circuits PG₀ and PG₁ ; and ○1 , ○2 , ○3 , and ○4 represent potential changes of the nodes ○1 , ○2 , ○3 , and ○4 in the circuit shown in FIG. 3.

The operation of the circuit shown in FIG. 3 will be described with reference to FIGS. 4A to 4F. In a state when no change occurs in any address bit or the chip select bit CS, the output signals φ₀, φ₁, . . . of the all pulse generating circuits PG₀, PG₁, . . . and PG_(n) are at the H level so that, as illustrated in FIG. 3 and in FIG. 4C, the node T₁ is L; the output ○2 of the inverter formed by the transistors Q₃ and Q₄ is H, as shown in FIGS. 3 and 4D. Accordingly, the transistor Q₇ is OFF; the transistor Q₉ is ON; the output ○3 of the CMOS inverter formed by the transistors Q₃₃ and Q₃₄ is H, as shown in FIG. 4E; the capacitor C is charged to V_(CC) ; the output ○4 of the inverter formed by the transistors Q₃₁ and Q₃₂ is L, as shown in FIG. 4F. Accordingly, the transistor Q₈ is ON and the transistor Q₁₀ is OFF. In the transistors Q₇ and Q₈, since the transistor Q₇ is OFF, the node T₁ is not pulled up to V_(CC). Also, in the transistors Q₉ and Q₁₀, since the transistor Q₉ is ON, the transistors Q₂₁, Q₂₂, . . . and Q.sub. 2n connected in series in the NAND gate, are connected through the transistor Q₉ to the ground power supply terminal V_(SS).

In this state, when either of the address bits, for example, A₁, is changed so that a pulse ○1 falls from H to L at a time t₁ as illustrated in FIG. 4B, the NAND gate generates H so that node T₁ becomes H as shown in FIG. 4C, and the output ○2 of the inverter formed by the transistors Q₃ and Q₄ becomes L. Therefore, the P-channel transistor Q₇ turns ON so that the node T₁ is pulled up to V_(CC) by the transistors Q₇ and Q₈ ; and the transistor Q₉ turns OFF so that the source of the transistor Q_(2n) is inhibited from being pulled down to V_(SS). Thus, the node ○2 of the clock signal generating circuit CG is latched to L; and, accordingly, the output end T₂ is latched to H. In this state also, the output ○3 of the inverter formed by the transistors Q₃₃ and Q₃₄ gradually decreases to L; and the output ○4 of the inverter formed by the transistors Q₃₁ and Q₃₂ becomes H at a time t₂ when the level at the node ○3 becomes lower than the threshold voltage of the P-channel transistor Q₃₁. Since the RC delay circuit formed by the resistor R and the capacitor C is included, the change of the level at the node ○4 includes the time delay td. When the output ○4 of the inverter formed by the transistors Q₃₁ and Q₃₂ becomes H after this delay, the P-channel transistor Q₈ turns OFF at a time t₃ so that the above-mentioned pulling up of the node T₁ is stopped, i.e., the latch is released; and the N-channel transistor Q₁₀ turns ON in response to the H level at the node ○4 so that the transistors Q₂₁, Q₂₂, . . . and Q_(2n) connected in series are connected through the transistor Q₁₀ to V_(SS). Accordingly, as long as the pulses from the pulse generating circuits are not present, that is, under the condition that all of the output signals φ₀, φ₁, . . . output from the pulse generating circuits PG₀, PG₁, . . . , and PG_(n) are at the H level, the node T₁ is pulled down to V_(SS) (L level), and, therefore, the node ○ 2 is raised to the H level at the time t₃ as shown in FIG. 4D. Thus, the output clock width of the clock signal generating circuit CG becomes a constant value determined by the RC time constant. Even when there are differences in the reset timings of the pulse φ₁, as illustrated by arrows in FIG. 4B, the output clock pulse at the node ○2 has a constant pulse width T.

There is a possibility of generation of two or more pulses output at slightly different timings from the pulse generating circuits PG₀, PG₁, . . . and PG_(n). As an example, FIGS. 4A and 4B show the two pulses φ₀ and φ₁ generated at different timings t₁ and t₄ from the pulse generating circuits PG₀ and PG₁. In this case, the pulse width of the pulse at the node ○2 is elongated, and, at the maximum, the pulse at the node ○2 terminates at a time t₅. The time period between the times t₄ and t₅ is equal to the time T determined by the RC delay circuit. The pulse at the node ○2 may be terminated before the time t₅ if the capacitor C is not fully charged at the time t₄.

FIG. 5 shows an example of one of the pulse generating circuits PG₀, PG₁, . . . , PG_(n-1), i.e., excluding the circuit PG_(n) which receives the chip select signal CS. In FIG. 5, AP is an input pad to which one of the address bits A₀, A₁, A₂, . . . is applied; Q₄₁, Q₄₃, Q₄₅, Q₄₇, Q₄₉, Q₅₁, Q₅₃, Q₅₅, Q₅₇, and Q₅₉ are P-channel MOS transistors; and Q₄₂, Q₄₄, Q₄₆, Q₄₈, Q₅₀, Q₅₂, Q₅₄, Q₅₆, Q₅₈, and Q₆₀ are N-channel MOS transistors. Pairs of transistors Q₄₁ and Q₄₂, Q₄₃ and Q₄₄, Q₅₃ and Q₅₄, and Q₅₅ and Q₅₆, constitute CMOS inverters, respectively. Groups of transistors Q₄₅, Q₄₆, Q₄₇ and Q₄₈ ; Q₄₉, Q₅₀, Q₅₁ and Q₅₂ ; and Q₅₇, Q₅₈, Q₅₉ and Q₆₀ constitute CMOS NAND gates, respectively.

The mutual conductances gm of the transistors Q₄₆, Q₄₈, Q₅₈ and Q₆₀ are made to be relatively small. On the contrary, the mutual conductances gm of the transistors Q₅₀ and Q₅₂ are made to be relatively large. Since the mutual conductances gm of the transistors Q₅₀ and Q₅₂ are relatively large, the output pulse φ at the node T₃ falls rapidly in response to a change of an address bit applied to the input pad AP. Also, since the mutual conductances gm of the transistors Q₄₆, Q₄₈, Q₅₈ and Q₆₀ are relatively small, the output pulse φ at the node N₃ rises a predetermined time later from the change of the address bit applied to the input pad AP.

In more detail, for example, when the potential at the input pad AP is at H, then the node N₁ is L; the node N₂ is H; the transistor Q₄₆ is ON; the node N₄ is H; the node N₅ is L; the node N₆ is H; the transistor Q₄₈ is ON; and, accordingly, the node N₃ is L and the output end T₃ is H. In this state, the node N₄ is H; the node N₅ is L; and the node N₆ is H; and the transistor Q₅₂ is on. From this state, when the address bit applied to the input pad AP turns to L, then the node N₁ becomes H; the node N₂ becomes L; the node N₃ becomes H; and the transistor Q₅₀ turns ON. Because of its large gm, the output end T₃ rapidly turns to the L level. Also, the node N₄ turns to L, and the node N₅ turns to H. The transistors Q₅₈ and Q₆₀ turn ON in response to the H levels at the nodes N₅ and N₃, respectively. However, since the mutual conductances of the transistors Q₅₈ and Q₆₀ are relatively small, the node N₆ gradually turns to the L level. Therefore, in response to the rapid operation of the transistor Q₅₀, the output end T₃ rapidly turns to the L level in response to a fall of the applied address bit. When the transistors Q₅₈ and Q₆₀ turn ON, the node N₆ gradually turns to the L level so that the transistor Q₅₂ becomes OFF. Thus, a predetermined time after the fall of the address bit, the output end T₃ rises again to the H level. The pulse width of the pulse obtained at the output end T₃ of the pulse generating circuit PG is determined by the values of the mutual conductances gm of the transistors Q₅₀, Q₅₂, Q₅₈, and Q₆₀ .

Similarly, when the potential at the input pad AP changes from L to H, a pulse having a pulse width corresponding to the difference in the mutual conductances gm of the transistors Q₅₀, Q₅₂ and Q₄₆, Q₄₈ is output at the output end T₃.

Since the mutual conductances gm of the transistors can not be determined accurately in the manufacturing process, the pulse width of the pulse at the output end T₃ is relatively indefinite because the timing of the rising edge is indefinite. Therefore, as illustrated in FIG. 4B by the arrows, the end of the pulse φ₁ is indefinite. This is the reason why the pulse generating circuit CG including the circuit WC as shown in FIG. 2 is necessary. Using the circuit shown in FIG. 2, a constant pulse width can be obtained regardless of the pulse widths applied from the pulse generating circuits PG₀, PG₁, . . . , and PG_(n).

FIG. 6 is a circuit diagram showing an example of the pulse generating circuit PG_(n) shown in FIG. 2. In FIG. 6, the circuit PG_(n) includes pairs of P-channel and N-channel transistors Q₆₁ and Q₆₂, Q₆₃ and Q₆₄, Q₆₅ and Q₆₆, and Q₇₁ and Q₇₂ which respectively constitute CMOS inverters. Q₆₉ is a P-channel transistor, and Q₇₀ and Q₇₃ are N-channel transistors. Q₆₇, Q₆₈, Q₆₉ and Q₇₀ constitute a CMOS NAND gate. This circuit PG_(n) also generates a pulse at an output end T₄ in response to a change from H to L of the chip select signal CS.

The pulse generating circuits PG₀, PG₁, . . . , and PG_(n) are not restricted to those for receiving the address bits A₀, A₁, A₂, . . . and the chip select signal CS. For example, a static random-access memory (RAM) is known in which a predetermined time after an address change, the selected word line is turned to the nonselected state (L level) to save power. In this case, when a write instruction is applied, the above-mentioned selected word line must be set to the H level during a necessary time. To do this, the pulse generating circuit must generate a pulse in response to a write enable signal WE.

The clock signal generating circuit CG is not restricted to the circuit shown in FIG. 2. Various variations are possible within the scope of the present invention. For example, the number of the CMOS inverters in the clock signal generating circuit may be arbitrarily selected in accordance with the desired output. If a pulse of H level is necessary, an additional inverter may be added. If a clock signal must be generated in response to a change from L to H of an input signal, this is also possible to those skilled in the art based on the circuit shown in FIG. 2. Further, in place of connecting the node T₁ to the gates of the transistors Q₃₃ and Q₃₄, the output of the inverter formed by the transistors Q₃ and Q₄ may be connected through an additional CMOS inverter to the gates of the transistors Q₃₃ and Q₃₄, or the output end T₂ may be connected to the gates of the transistors Q₃₃ and Q₃₄. Still further, in place of the output end T₂, the output of the CMOS inverter formed by the transistors Q₃ and Q₄ may be used as the output end of the clock signal generating circuit CG.

From the foregoing description, it will be apparent that, according to the present invention, a clock signal having a constant pulse width regardless of the pulse widths of the input signals can be generated, which is effective for use in a static memory. 

I claim:
 1. A semiconductor circuit operatively connected to a power supply having first and second terminals of opposite polarity, comprising:at least one input-change detecting circuit, operatively connected to the first and second terminals of the power supply, having a first output end for generating a pulse in response to a change of an input signal; a gate circuit, operatively connected to the first and second terminals of the power supply, having an input end operatively connected to said first output end and having a second output end, for changing an output signal when the input signal changes; an inverter, operatively connected to said second output end and the first and second terminals of the power supply, having a third output end; and a pulse-width fixing circuit, operatively connected to the first and second terminals of the power supply and said second output end of said gate circuit, for latching the output signal of said gate circuit in response to a signal change at said second output end of said gate circuit and for resetting the output signal a predetermined time after the onset of the latching, comprising:first and second transistors connected in series between the first terminal of the power supply and said second output end of said gate circuit, said first and second transistors having gate electrodes, the gate electrode of said first transistor operatively connected to said third output end; reset means, operatively connected to the gate electrode of said second transistor, for resetting the latching after a predetermined time delay from the onset of the latching; and a control circuit, operatively connected to the first and second terminals of the power supply, having an input end connected to said second output end and having a reset output end connected to said reset means, said control circuit including a delay circuit for transferring a signal change at said input end of said control circuit to said reset output end with the predetermined time delay to control said reset means.
 2. A semiconductor circuit as set forth in claim 1, wherein said input-change detecting circuit is operatively connected to receive an address signal for accessing a memory device.
 3. A semiconductor circuit as set forth in claim 1, wherein said input-change detecting circuit is operatively connected to receive a chip select signal for selecting a memory chip of a memory device.
 4. A semiconductor circuit as set forth in claim 1,wherein said semiconductor circuit further comprises a memory device, operatively connected to the power supply and to said gate circuit, for performing a write operation,and wherein said input-change detecting circuit is operatively connected to receive a write enable signal for enabling the write operation of the memory device.
 5. A semiconductor circuit as set forth in claim 1, wherein said pulse-width fixing circuit generates a pulse having a constant pulse width.
 6. A semiconductor circuit as set forth in claim 1, wherein said resetting means comprises:a third transistor having a gate electrode connected to said third output end of said inverter; and a fourth transistor having a gate electrode connected to said reset output end of said control circuit, said third and fourth transistors being connected in parallel between said gate circuit and the second terminal of the power supply.
 7. A semiconductor circuit as set forth in claim 6, wherein said control circuit comprises:a first inverter, operatively connected to the first terminal of the power supply, having an input end connected to said second output end of said gate circuit and having a fourth output end; a second inverter, operatively connected to the first and second terminals of the power supply, having an input end connected to the fourth output end of said first inverter and having an output end connected to the gate electrodes of said second transistor and said fourth transistor; a resistor connected between said first inverter and the second terminal of the power supply; and a capacitor connected between the fourth output end of said first inverter and the ground power supply, said resistor and said capacitor forming said delay circuit.
 8. A semiconductor circuit operatively connected to a power supply, comprising:at least one input-change detecting circuit, operatively connected to the power supply, having a first output end for generating a pulse in response to a change of an input signal; a gate circuit, operatively connected to the power supply, having an input end operatively connected to said first output end and having a second output end, for changing an output signal when the input signal changes; and a pulse-width fixing circuit, operatively connected to the power supply and said second output end of said gate circuit, for latching the output signal of said gate circuit in response to a signal change at said second output end of said gate circuit and for resetting the output signal a predetermined time after the onset of the latching, said pulse-width fixing circuit comprising:latching means for latching the signal change at said output end; a control circuit, operatively connected to the power supply, having an input end connected to said output end of said gate circuit and having a reset output end, said control circuit including a delay circuit for transferring a signal change at said input end of said control circuit to said reset output end with a predetermined time delay; and first and second transistors connected in parallel between said gate circuit and the power supply, said first transistor having a control terminal operatively connected to said second output end and said second transistor having a control terminal operatively connected to said reset output end of said control circuit. 